(a) Field of the Invention
The present invention relates generally to a flat panel display, and more particularly to an apparatus and a method for driving the flat panel display.
(b) Description of the Related Art
A typical flat panel display in commercial use includes a liquid crystal display (LCD) and a plasma display panel (PDP) and, in addition, such display as an electro luminescence (EL) has been developed.
A flat panel display module has a flat panel in which pixels are arranged in a matrix form between two glass substrates, a PCB (printed circuit board) module for driving the flat panel, and a case for protecting and integrating them.
As shown in FIG. 1 illustrating an entire circuit configuration of a typical flat panel display module, the PCB module for driving the flat panel 40 typically includes a main PCB 10 for receiving RGB image data, synchronization signals, etc., from an external apparatus like a PC. Such signals are processed by a timing controller T-con, a customized integrated circuit in the form of FPGA (flat pin grid array), so that image data and a variety of control signals are produced in accordance with structure of the flat panel 40. It also includes a row driver 20 for supplying scanning signals for row signal lines based on row driver control signals 50 and power signals 51 received from the main PCB 10, and a column driver 30 for supplying gray level voltages 61 for the flat panel 40 after receiving the image data and the control signals 60 processed in the main PCB and the gray level voltages 61.
However, as conventional driving circuits implemented on the main PCB 10 have a masking timing setting scheme that combines timing and various input driving interface conditions within a specification prescribed for the panel, it is impossible to modify timing and operation of the driving circuits depending on the changes of user conditions and input conditions of display source and monitor product. In other words, the timing and operation of the driving circuits are fixed, and even within a range of possible operation, it is impossible to flexibly support the optimization of display characteristics unless processed by a hardware option in the driving circuits. This is because the timing conditions for input of the flat panel display is basically set to be suitable for VESA specification, and allows a graphic source to produce and display digital interface timing control signals for driving the panel on the basis of digital data communication (DDC) information stored in the flat panel display module. In addition, flat panel display monitor products on the market set gamma voltages and various power sources for differentiating gray.
According to the conventional art, a user can adjust gamma voltages, flicker voltages, brightness, scaling, frame rate control (FRC), I/O format, etc., by identifying and adjusting a screen display state using an On Screen Display (OSD) function or directly adjusting a hardware. However, only by using these functions, although an optimal screen can be driven by modifying timing (modifying a driving frequency or modification to least and optimal blanking time) on the flat panel driving circuit or a very good driving environment can be achieved by processing a standard signal through an additional circuit in the graphic source so that the driving frequency is modified or the modification to the least and optimal blanking time is made, as referred to above, as an I/O format is required to satisfy the requirement to a general display standard, however good the above conditions may be, a risk to the modification is very high.
In addition, particularly, an interface is required to drive a different I/O format of display source for use in a monitor, and if a difference occurs in a frame frequency or the number of blanking interval, an additional system board (such option board as A/D board, D/D board, etc.), which is capable of FRC adjustment, should be supported. Furthermore, the I/O format of the flat panel display is limited and efficiency of the display products cannot be fully facilitated. Furthermore, a jitter caused by the option board and a mismatch of bi-directional interface conditions result in poor picture quality. It neither contributes to optimizing the monitor products.
As described above, a difference in display manner from a CRT display and the flat panel display causes this problem. The CRT can drive widely up to from 40 Hz to 85 Hz in the frame frequency while the driving manner of the flat panel display is determined by the characteristics of the panel. In other words, if the characteristics of the current panel is optimized at the frame frequency of 60 Hz, the driving conditions also becomes necessarily optimized at 60 Hz. In addition, since a graphic card or the display source does not exactly follow a VESA standard, different manufacturers supply data of various timing slightly different from standard timing. Therefore, when the timing for the optimal driving conditions of the flat panel should be different from the timing of the VESA standard signal or a slight deviation occurs in the standard signal dependent on manufacturers, though an additional option board is used in order to adjust such a changeable timing, this is insufficient to perform completely the function described above and the additional board incurs a high cost.
In addition, a blanking interval (horizontal synchronization signal, back porch, front porch)) taken to return to the next line after line of electron beam is scanned with the standard of input timing of VESA display as the CRT standard and a blanking interval (vertical synchronization signal, back porch, front porch) taken to return from last position, where one frame is scanned, to first position are specified for each frequency. However, since an active matrix scheme and the like other than a scanning scheme are used in driving the flat panel, after transfer of last display signal of line or frame, a blanking interval may have only a blanking interval of as much as least pixel (in case of a horizontal blanking) or line (in case of a vertical blanking), unlike the CRT. In addition, by using such option board as an A/D board, when the operation frequency is increased and the blanking interval becomes long and unstable so that an interface process or an I/O becomes unstable due to an unnecessary blanking interval in the VESA conditions, the driving conditions of the flat panel also becomes considerably unstable. Accordingly, there is a need that the flat panel can be driven on optimal driving timing conditions by reducing the blanking time described above so that display characteristics becomes stable and reliable.
In addition, there is a case that the display characteristics should be adjusted based on product tolerance or user environment and conditions. As these flat panel monitor products are conventionally set with the optimal driving conditions determined by the characteristic of the flat panel, an adjustment should be made by an additional option board or an interface board. However, by adjustment of gamma, contrast, brightness, flicker, and other display characteristics, when the optimal driving conditions fixed in accordance with characteristic of the flat panel is modified, there were the problems that the flat panel characteristics can be used with 100% efficiency since contrasted upper and lower gray levels are fitted to the flat panel in a truncated state by clamping when the A/D board or the option board is used.
Therefore, there is a desirable need to provide an essential driving scheme that eliminates cost rise due to the option board as well as prevents the jitter caused by the mismatch of interface conditions. In other words, there is a need to facilitate the modification to FRC, I/O format, and other information on the display characteristics so that resolution information, information on such operation frequency as vertical and horizontal frequency of the picture signal and main frequency of the picture signal, as well as digital information on gamma voltage, flicker voltage, and brightness and the like can be shared by the graphic source and the flat panel display module can be updated by users. Particularly, there is a need to utilize the signal outputted from the graphic source to the maximum so that it is adapted to the driving of the flat panel display device by using the signal as the standard signal as well as the picture signal modified in its blanking interval and then its frequency based on a definition by the user.